Half-sandwich complexes of iridium and ruthenium containing cysteine-derived ligands. Issue 3 (23rd December 2016)

• Record Type: Journal Article
• Authors: Carmona, María; Rodríguez, Ricardo; Lahoz, Fernando J.; García-Orduña, Pilar; Cativiela, Carlos; López, José A.; Carmona, Daniel
• Is Part Of: Dalton transactions. Volume 46:Issue 3(2017)
• Page Start: 962
• Page End: 976
• Publication Date: 2016-12-23
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt04341k
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Modified cysteines display five distinct coordination modes towards (C5 Me5 )Ir and (η 6 - p -MeC6 H4 iPr)Ru moieties. From spectroscopic and crystallographic data, the absolute configuration of the resulting chiral compounds has been established. Abstract : The dimers [{(η n -ring)MCl}2 (μ-Cl)2 ] ((η n -ring)M = (η 5 -C5 Me5 )Ir, (η 6 - p -MeC6 H4 iPr)Ru) react with the modified cysteines S -benzyl-l -cysteine (HL1 ) or S -benzyl-α-methyl-l -cysteine (HL2 ) affording cationic complexes of the formula [(η n -ring)MCl(κ 2 N, S -HL )]Cl (1, 2 ) in good yield. Addition of NaHCO3 to complexes1 and2 gave equilibrium mixtures of neutral [(η n -ring)MCl(κ 2 N, O -L )] (3, 4 ) and cationic [(η n -ring)M(κ 3 N, O, S -L )]Cl (6Cl, 7Cl ) complexes. Similar mixtures were obtained in one-pot reaction by successive addition of the modified cysteine and NaHCO3 to the above formulated dimers. Addition of the N -Boc substituted cysteine derivative S -benzyl- N -Boc-l -cysteine (HL3 ) and NaHCO3 to the dimers [{(η n -ring)MCl}2 (μ-Cl)2 ] affords the neutral compounds [(η n -ring)MCl(κ 2 O, S -L3 )] ((η n -ring)M = (η 5 -C5 Me5 )Ir (5a ), (η 6 - p -MeC6 H4 iPr)Ru (5b )). Complexes of the formula [(η n -ring)MCl(κ 3 N, O, S -L )][SbF6 ] (6Sb–8Sb ), in which the cysteine derivative acts as a tridentate chelate ligand, can be prepared by adding one equivalent of AgSbF6 to the solutions of compounds5 or to the mixtures of complexes3 /6Cl and4 /7Cl . The amide proton of compounds8aSb and8bSb can be removed by addition of NaHCO3 affording the neutral complexes [(η n -ring)M(κ 3 N, O, S -L3-H )] ((η n -ring)M = (η 5 -C5 Me5 )Ir (9a ), (η 6 - p -MeC6 H4 iPr)Ru (9b )). Complexes9a and9b can also be prepared by reacting the dimers [{(η n -ring)MCl}2 (μ-Cl)2 ] withHL3 and two equivalents of NaHCO3 . The absolute configuration of the complexes has been established by spectroscopic and diffractometric means including the crystal structure determination of ( R Ir, R C, R S )-[(η 5 -C5 Me5 )Ir(κ 3 N, O, S -L1 )][SbF6 ] (6aSb ). The thermodynamic parameters associated with the epimerization at sulphur that the iridium compound [(η 5 -C5 Me5 )Ir(κ 3 N, O, S -L3-H )] (9a ) undergoes have been determined through variable temperature 1 H NMR studies.